EP2380782A1 - Front structural assembly for a vehicle and related engine mounting extensions - Google Patents

Abstract

The assembly has a longitudinal frame extension (10) connecting a transverse low area bumper beam with a body shell of a motor vehicle. The extension has intersecting ribs (14, 15) extended on an outer face (24) of an elongated tubular body (12). The ribs and the tubular body are made of same material. A ribbed fixation base (17) is arranged at an end of the body. The fixation base and the tubular body are made of same material. A central recess (20) traverses the tubular body, and is opened at longitudinal ends of the tubular body. The frame extension is made of plastic or composite material. An independent claim is also included for a method for fabricating a cradle frame extension of a frontal structural assembly of a motor vehicle.

Description

• un corps allongé comportant une face extérieure ;
• des nervures entrecroisées s'étendant sur la face extérieure du corps, les nervures étant venues de matière avec le corps ; et
• au moins une embase de fixation, située à une extrémité du corps, l'embase de fixation étant venue de matière avec le corps.

The present invention relates to a front structural assembly of a motor vehicle, of the type comprising a lower transverse bumper beam and longitudinal extensions for connecting the bumper beam to the body of the motor vehicle, the extensions each comprising:

• an elongate body having an outer face;
• intersecting ribs extending on the outer face of the body, the ribs being integral with the body; and
• at least one attachment base, located at one end of the body, the fixing base being integral with the body.

• assurer la protection des occupants du véhicule, notamment en cas de choc frontal ;
• maîtriser les coûts de réparation du véhicule, notamment suite à un choc à faible vitesse ; et
• limiter l'agressivité du véhicule vis-à-vis des autres usagers de la route, et notamment des piétons.

In the context of passive safety, which concerns all the means and actions implemented to reduce the consequences of an accident, car manufacturers have to face three major concerns:

• protect the occupants of the vehicle, particularly in the event of a frontal impact;
• control the costs of repairing the vehicle, particularly following a low-speed impact; and
• limit the aggressiveness of the vehicle vis-à-vis other road users, including pedestrians.

For this, the new motor vehicles have a front structure, including including main beams carrying a cross bumper ("high road"). This high track is lined with a front structural assembly comprising a cradle supporting the front suspension of the vehicle and a transverse bumper beam, located at a height lower than that of the bumper beam and connected to each of its ends. in the cradle by an extension ("low way").

Such a structural assembly absorbs part of the energy of the frontal shocks and allows a better distribution of the energy of these shocks at the level of the vehicle body; it thus contributes to a better repairability of the vehicle. In addition, the transverse beam, in case of frontal impact with a pedestrian, reduces the risk of serious injury to the legs of the pedestrian.

EP 1 955 930 discloses such a front structural assembly comprising extensions of composite material.

However, this front structural assembly has a number of drawbacks related to its embodiment, particularly penalizing the behavior during high speed impacts. Indeed, this profile is not ideal to reconcile a good compressive holding of extensions with acceptable wall thicknesses and mass.

An object of the invention is therefore to provide a better compromise through a lightweight front assembly and having a satisfactory compressive strength.

For this purpose, the subject of the invention is a front structural assembly of a motor vehicle of the aforementioned type, characterized in that the body of each extension is tubular and comprises at least one recess passing through the body and opening at its longitudinal ends.

• au moins une nervure s'étend longitudinalement le long du corps ;
• au moins une nervure s'étend transversalement ;
• les prolonges sont en matériau plastique ou composite ;
• chaque prolonge est monobloc ;
• le corps de chaque prolonge est formé de deux tronçons tubulaires tronconiques convergeant l'un vers l'autre ;
• chaque prolonge est constituée de deux demi-coques allongées de forme générale semi-cylindrique ;
• les demi-coques sont liées continument l'une à l'autre par un pont de matière faisant charnière ;
• la ou chaque embase est nervurée ; et
• il comprend un berceau, notamment un berceau moteur, destiné à être fixé sur la caisse d'un véhicule automobile, les prolonges définissant des prolonges de berceau.

The front structural assembly according to the invention may comprise one or more of the following features, taken in isolation or in any technically possible combination (s):

• at least one rib extends longitudinally along the body;
• at least one rib extends transversely;
• the extensions are made of plastic or composite material;
• each extension is monoblock;
• the body of each extension is formed of two frustoconical tubular sections converging towards one another;
• each extension consists of two elongated half-shells of generally semi-cylindrical shape;
• the half-hulls are connected continually to one another by a bridge of material hinge;
• the or each base is ribbed; and
• it includes a cradle, including a motor cradle, intended to be fixed on the body of a motor vehicle, the extensions defining cradle extensions.

The invention also relates to a method of manufacturing a cradle extension for such a front structure of a motor vehicle, characterized in that a composite or plastic material is injected into a mold so as to form the extension.

• des noyaux, notamment tronconiques, sont introduits dans le moule avant injection du matériau constitutif de la prolonge, de façon à former l'évidement central de la prolonge ; et
• un fluide liquide est injecté dans le moule pendant l'injection du matériau constitutif de la prolonge, de façon à former le ou chaque évidement de la prolonge.

The method according to the invention can comprise one or more of the following characteristics, taken alone or in any combination (s) technically possible (s):

• cores, in particular frustoconical, are introduced into the mold before injection of the material constituting the extension, so as to form the central recess of the extension; and
• a liquid fluid is injected into the mold during the injection of the material constituting the extension, so as to form the or each recess of the extension.

• la Figure 1 représente une vue en perspective de trois-quarts avant d'un ensemble structurel avant de véhicule automobile selon l'invention ;
• la Figure 2 représente une vue en perspective d'une prolonge de l'ensemble structurel avant de la Figure 1 ;
• la Figure 3 représente une vue de face d'une prolonge selon une variante de la prolonge de la Figure 2 ;
• la Figure 4 représente une vue en coupe longitudinale d'une prolonge selon une autre variante de la prolonge de la Figure 2 ;
• la Figure 5 représente une vue éclatée en perspective d'une prolonge selon deuxième mode de réalisation ;
• la Figure 6 représente une vue en coupe transversale d'une prolonge selon une variante de la prolonge de la Figure 5 ;
• la Figure 7 représente une vue en coupe longitudinale de la prolonge de la Figure 4, lors de sa fabrication.

The present invention will be better understood on reading the description which follows, given solely by way of example, and with reference to the appended drawings, in which:

• the Figure 1 represents a perspective view of three-quarters front of a front structural assembly of a motor vehicle according to the invention;
• the Figure 2 represents a perspective view of an extension of the structural assembly before the Figure 1 ;
• the Figure 3 represents a front view of a prolongation according to a variant of the extension of the Figure 2 ;
• the Figure 4 is a longitudinal sectional view of an extension according to another variant of the extension of the Figure 2 ;
• the Figure 5 represents an exploded perspective view of a continuation according to the second embodiment;
• the Figure 6 represents a cross-sectional view of an extension according to a variant of the extension of the Figure 5 ;
• the Figure 7 represents a longitudinal sectional view of the extension of the Figure 4 , during its manufacture.

In all that follows, the terms "left" and "right" refer to the usual orientations and to the normal direction of operation of a motor vehicle, illustrated by the arrow S on the Figure 1 .

The structural assembly before 1 of a motor vehicle represented on the Figure 1 comprises a cradle 5 of the automobile body, a transverse beam 7 and extensions 9, 10.

The cradle 5 is for example a motor cradle. It extends substantially horizontally, under the main rails of the vehicle body. It supports at least in part the suspensions of the front wheels of the vehicle, as well as the engine. It also serves as attachment to the arms of the suspensions and / or the anti-roll bar.

The transverse beam 7 is a low track bumper beam. It extends over most of the width of the vehicle. It is arranged below the main bumper beam supported at the end of the main beams, at a height above the ground below the knee height of a pedestrian average size.

The extensions 9, 10 are made of composite material (fiber-reinforced plastic material) or plastic material and connect the right and left ends of the beam 7 to the element 5.

The extensions 9, 10 are independent of each other. As a variant, they are integral with a fairing plate extending substantially horizontally and constitute, with this plate, a structural fairing. Preferably, the fairing plate then comprises access devices to the mechanics of the vehicle, such as traps.

The extensions 9, 10 are analogous and symmetrical with respect to a median vertical longitudinal plane of the vehicle. Only the extension 10 right (left on the Figure 1 ) will be described in more detail, with reference to the Figure 2 .

The extension 10 is monobloc. It comprises a tubular body 12, elongated in a direction of extension L close to the longitudinal axis of the vehicle, a set of ribs 14, 15 and bases 17, 18 for fixing.

The body 12 has a substantially constant cross section along its entire length. It comprises a single central recess 20 and a wall 21, said wall 21 having an inner face 22 and an outer face 24.

The central recess 20 extends longitudinally and passes through the body 12 in the direction of extension L. The central recess 20 opens at the ends of the body 12.

The wall 21 is of substantially equal thickness at all points.

The ribs 14, 15 extend on the outer face 24 of the wall 21 of the body 12. They are integral with the body 12. They have a geometry adapted to oppose the buckling of the extension along its longitudinal axis. In the case presented, they are, for example, intersecting. Longitudinal ribs 14, intended to increase the inertia of the profile, extend longitudinally along the body 12. Transverse ribs 15, intended to stabilize the longitudinal ribs 15 during their deformation, extend transversely.

Each base 17, 18 is rigid and integral with the body 12. Each base 17, 18 has an inner face 32 facing the body 12, an outer face 34 facing the opposite of the body 12, a through hole 36 and fastening means 38 to the cradle 5 or to the beam 7.

The outer face 34 of each base 17, 18 is ribbed.

The orifice 36 of each base 17, 18 opens on one side into the outer face 34 and on the other side into the inner face 32, inside the recess 20.

The fastening means 38 of each base 17, 18 are, for example, through openings suitable for the passage of rivets or fixing screws.

The variant presented on the Figure 3 differs from that of Figure 2 in that the single central recess 20 is replaced by an inner cellular reinforcing structure 40, comprising a multitude of recesses or veins 42 extending longitudinally in the extension direction L and passing through the body 12. The structure internal 40 is reported in the housing, for example in the form of a honeycomb insert, or is integral with the body 12.

The variant presented on the Figure 4 , differs from that of the Figure 2 in that the body 12 does not have a constant cross section, but is formed of two frustoconical tubular sections 46, 47 converging towards one another. The widest ends of these tubular sections are opposite and form the ends of the body 12. The ribs, increasing in height as close to the middle of the body 12, extend radially between the wall 21 and a cylindrical outer envelope.

A second embodiment of the extension 10 is presented on the Figure 5 . The extension 10 is then not made of a one-piece assembly, but two half-shells welded, for example by friction or ultrasound, or adhered: a first half-shell 50 and a second half-shell 51. Each half -coque 50, 51 comprises two half-bases, respectively 54, 55 and 56, 57 an elongated hollow half-cylinder 60, 61 having an outer face 64, 65, ribs 68, 69 extending on the outer face 64, 65 of the half-cylinder 60, 61 and two elongated flanges respectively 70, 71 and 72, 73. Preferably, each half-shell 50, 51 also comprises at least one element 75, 76 of relative positioning.

The elongated flanges 70, 71 extend longitudinally along the half-cylinder 60. They are coplanar, located in the same plane P. The entire first half-shell 50 extends on one side of the plane P.

The elongated flanges 72, 73 extend longitudinally along the half-cylinder 61. They are coplanar, located in the same plane P '. All the second half-shell 51 extends on one side of the plane P '.

Each elongated flange 70, 71, 72, 73 is planar and has a rectilinear transverse profile, without a slot.

The variant presented on the Figure 6 differs from that of Figure 5 in that each elongated flange 70, 71, 72, 73 has a crenellated transverse profile. Each elongated flange 70, 71, 72, 73 comprises at least two bearings, an outer bearing respectively 80, 81, 82, 83 and an inner bearing respectively 84, 85, 86, 87, at different heights, separated by a recess. The profiles of the elongated flanges 70 and 71 on the one hand, 72 and 73 on the other hand are symmetrical with respect to a longitudinal plane perpendicular to the plane P, respectively perpendicular to the plane P '. The elongated flanges 70, 71 of the first half-shell 50 have a shape complementary to that of the elongated flanges 72, 73 of the second half-shell 51.

For example, the outer bearings 80, 81 of the elongated flanges 70, 71 of the first half-shell 50 are both at a height less than that of the bearings 84, 85, and the outer bearings 82, 83 of the elongated flanges 72, 73 of the second half-shell 51 are both at a height greater than that of the inner bearings 86, 87, the height deltas between the outer bearings 80, 81, 82, 83 and the inner bearings 84, 84, 86, 87 being in each case the same.

When the half-shells 50, 51 are in contact along their elongate edges 70, 71, 72, 73, they together form a prolongation similar to the extension of the Figure 2 : the half-bases 54, 56 on the one hand, 55, 57 on the other hand, form the bases 17, 18, the two half-cylinders 60, 61 form the body 12 and the elongate edges 70, 72 of a part, 71, 73 on the other hand, form longitudinal ribs.

Optionally, the half-shells 50, 51 are connected by a bridge of flexible material along one of the 70, 72 of their elongated flanges 70, 71, 72, 73. This material bridge is integral with each of the half-shells 50, 51.

In the case where the extensions 9, 10 are part of a structural fairing, only one of the half-shells 50, 51 is integral with the fairing plate.

We will now describe the manufacturing process of the extension 10.

According to a first embodiment, the extension is formed in a single mold. This mold has an inner cylindrical wall in which are formed trenches, some extending longitudinally along the inner wall and others extending transversely, vertical walls closing the mold at the ends of the cylindrical wall. The mold also comprises a plastic or composite material injection nozzle and a fluid injection nozzle, both formed in one of the vertical walls.

A composite or plastic material is injected into the mold by the injection nozzle of plastic or composite material. Then a fluid under pressure, preferably a liquid, is injected in turn by the fluid injection nozzle. This fluid forms a bubble in the previously injected material and compact the latter against the cylindrical wall of the mold. This bubble gives birth to the central recess 20. After demolding, we obtain a prolongation similar to that of the Figure 2 .

In a variant, the mold comprises a plurality of fluid injection nozzles. The pressurized fluid is then injected at several points of one of the vertical walls. It then forms several bubbles in the composite material or plastics, bubbles that give rise to the veins 42 represented on the Figure 3 .

According to a second embodiment, the composite or plastic material is injected into a mold 100 represented on the Figure 7 . Frustoconical cores 104, 105 are placed in the mold 100 so that they converge towards each other. The cores 104, 105 are in contact along their ends 108, 109 of smaller diameter. Their ends 111,112 larger diameter out of the mold 100.

The composite or plastic material injected into the mold 100 is distributed throughout the mold 100, with the exception of the space occupied by the cores 104, 105. The material is distributed around the cores 104, 105.

Once the material stiffened, it is removed from the mold. The cores 104, 105 are removed. This coring operation is simplified by the frustoconical shape of the cores 104, 105. Finally, a prolongation 10 similar to the variant presented on FIG. Figure 4 .

According to a third embodiment, the composite or plastic material is injected into two molds each having a general shape of hollow half-cylinder. These injections are preferably carried out separately. The material is injected to completely fill each of the two molds.

Alternatively, the molds are located parallel to each other, close to each other, so that they are flush along an edge. In this case, the injection is carried out simultaneously in the two molds, so that the material completely fills each of the molds. During this injection, material flows through the outcrop and forms a material bridge between the two molds.

Once the material is stiffened, the two half-shells 50, 51 thus formed are demolded. They are then placed facing each other, so that the flanges 70, 72 on the one hand, 71, 73 on the other hand, face each other. The relative positioning elements 75, 76, as well as possibly the material bridge, help the positioning of the half-shells 50, 51 relative to one another. The half-shells 50, 51 are finally glued to each other along their elongate edges 70, 71, 72, 73. Alternatively, they are welded, for example by friction or ultrasound.

Even if the front structural assembly according to the invention has been described as having a cradle on which the extensions are fixed, the invention is not limited to this single embodiment. It is indeed possible to fix the extensions to any element of a motor vehicle body, without departing from the scope of the invention.

Thanks to the invention, the compressive strength of the extensions is improved, especially thanks to the hollow body, which comprises a single central recess or a plurality of parallel channels or veins passing through the body along its entire length.

In addition, the wall of the body being of constant thickness, this allows a better stability of the extension in compression in case of frontal impact.

In addition, the use of external ribs strengthens the resistance of the buckling and flexion extension, and easy adaptation of its energy absorption characteristics.

Finally, the composite or thermoplastic materials employed make it possible to obtain a light structure that will avoid weighing down the vehicle on which the extensions are mounted and, since the extensions are in one piece, the number of parts required during the assembly of the vehicle is reduced.

Claims (13)

Front structural assembly (1) of a motor vehicle comprising a transverse bumper beam (7) for a lower track and longitudinal extensions (9, 10) for connecting the bumper beam (7) to the body of the motor vehicle, the extensions (9,10) each comprising: - an elongate body (12) having an outer face (24); - intersecting ribs (14, 15) extending on the outer face (24) of the body (12), the ribs (14, 15) being integral with the body (12); and - At least one fixing base (17, 18), located at one end of the body (12), the fixing base (17, 18) being integral with the body (12); characterized in that the body (12) of each extension (9, 10) is tubular and comprises at least one recess (20, 42) passing through the body (12) and opening at its longitudinal ends. Front structural assembly of a motor vehicle according to claim 1, characterized in that at least one rib (14) extends longitudinally along the body. Front structural assembly of a motor vehicle according to any one of claims 1 or 2, characterized in that at least one rib (15) extends transversely. Front structural assembly of a motor vehicle according to any one of the preceding claims, characterized in that the extensions are made of plastic or composite material. Front structural assembly of a motor vehicle according to any one of the preceding claims, characterized in that each extension (9, 10) is in one piece. Front structural assembly of a motor vehicle according to claim 5, characterized in that the body (12) of each extension (9, 10) is formed of two frustoconical tubular sections (46, 47) converging towards one another. Front structural assembly of a motor vehicle according to any one of claims 1 to 4, characterized in that each extension (9, 10) consists of two half-shells (50, 51) elongated generally semi-cylindrical shape. Motor vehicle front structural assembly according to claim 7, characterized in that the half-shells (50, 51) are continuously connected to each other by a hinge material bridge. Front structural assembly of a motor vehicle according to any one of the preceding claims, characterized in that the or each base (17, 18) is ribbed. Front structural assembly of a motor vehicle according to any one of the preceding claims, characterized in that it comprises a cradle (5), in particular a motor cradle intended to be fixed to the body of a motor vehicle, the extensions (9, 10) defining cradle extensions. A method of manufacturing a cradle extension (10) for a front structural assembly of a motor vehicle according to any one of claims 1 to 10, characterized in that a composite or plastic material is injected into a mold (100) of to form the extension (10). Manufacturing method according to claim 11, characterized in that cores (104, 105), in particular frustoconical cores, are introduced into the mold (100) before injection of the constituent material of the extension (10), so as to form the recess central (20) of the extension (10). Manufacturing method according to claim 11, characterized in that a liquid fluid is injected into the mold (100) during the injection of the constituent material of the extension (10), so as to form the or each recess (20, 42 ) of the extension (10).

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